Electrochemical firing device

ABSTRACT

A firing device wherein an electroresponsive explosive primer is constrained in an &#39;&#39;&#39;&#39;out-of-circuit&#39;&#39;&#39;&#39; position by an electrolytically controlled delay device. The circuit includes several electrolytically timed normally open switches which prevent the initiation of the primer until a predetermined length of time has elapsed whereupon the switches close and complete the circuit allowing a charged capacitor to discharge through the primer thereby initiating detonation.

United States Patent [1 1 Hinely et al.

[ Dec. 18, 1973 ELECTROCHEMICAL FIRING DEVICE [75] Inventors: Douglas M. Hinely, Derwood;

Robert J. Lyon, Silver Spring, both of Md.

[73] Assignee: The United States of America as represented by the Secretary of the Navy, Washington, DC.

[22] Filed: Apr. 15, 1971 [21] Appl. No.: 134,171

[52] U.S. Cl l02/70.2 R [51] Int. Cl. F421) 5/08, F23q 7/02 [58] Field of Search 102/702 R; 317/80 [56] References Cited UNITED STATES PATENTS 2,892,128 Wolf 317/80 9/1965 Lyon 102/702 R 1/1970 Offie 102/702 R Primary ExaminerBenjamin A. Borchelt Assistant Examiner.l. V. Doramus Attorney-R. S. Sciascia, J. A. Cooke, R. J. Erickson and M. G. Raskin [57] ABSTRACT A firing device wherein an electroresponsive explosive primer is constrained in an out-of-circuit position by an electrolytically controlled delay device. The circuit includes several electrolytically timed normally open switches which prevent the initiation of the primer until a predetermined length of time has elapsed whereupon the switches close and complete the circuit allowing a charged capacitor to discharge through the primer thereby initiating detonation.

5 Claims, 5 Drawing Figures PAIENIEB nu: 18 I975 SHEET 2 [IF 2 1 N VEN TORS Douglas M Hinely Robert JL yon ELECTROCHEMICAL FIRING DEVICE BACKGROUND OF THE INVENTION This invention relates generally to delay actuation devices and more particularly to a delay firing device wherein the delay is accomplished by electrolytic timing cells.

In the past it has been the practice to use mechanical watch-type escapement mechanisms in time delayed arming and firing fuzes for ordnance equipment such, for example, as mines. Such mechanisms have oftentimes proven to be unsatisfactory for various reasons such, for example, as their tendency to jam under extremely adverse handling conditions. The intricate gearing arrangement of the escapement sometimes prevents the mechanism from completing a cycle of operations sufficient to arm the mine. Further, the shelf-life of escapement type fuzes is limited because periodic cleaning and reoiling is necessary to maintain its operation.

Other time delay fuzes incorporate water soluble elements to provide a time delay between the actuation, the arming and the detonation of a mine. This type of device suffers from the deficiency that the dissolving time of the soluble substance tends to vary considerably depending upon various parameters such as water temperature, salinity current flow rate, etc. Another problem inherent in both the escapement and water soluble prior art devices is that, in general, these devices cannot be adapted to effect relatively long delays, such for example, as a week, between actuation and arming of the associated ordnance device.

SUMMARY OF THE INVENTION Accordingly, one object of this invention is to provide a new and improved delay actuation device.

Another object of the invention is the provision of a new and improved delay firing device in which the delay is effected by an electrolytic device.

Still another object of the present invention is to provide a new and improved electrolytically delayed fuze which will function under extremely adverse conditions.

A further object of the instant invention is to provide a new and improved delay fuze which has a relatively great shelf-life.

A still further object of this invention is the provision of a new and improved accurate time delay fuze for use in underwater ordance.

' Another still further object of the instant invention is the provision of a delay fuze which may provide a relatively long accurate delay period.

Briefly, in accordance with one embodiment of this invention, these and other objects are attained by providing a device having a normally open discharge circuit with an explosive primer movably positioned in an out-of-circuit position which is shifted into an in-circuit position a predetermined time after the actuation of the device. A fixed time after this shift the discharge circuit is closed thereby initiating the primer charge. Electrolytically controlled timing devices control both the movement of the primer from the out-of-circuit position to the in-circuit position and the closing of the discharge circuit.

BRIEF DESCRIPTION OF THE DRAWING A more complete appreciation of the invention and many of the attendant advantages thereof will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

FIGS. 1 a and b are side-sectional views of an electrolytic primer moving device and an electrolytic switch, respectively, used in the present invention;

FIG. 2 is a diagrammatic view of a circuit arrangement which may comprise the present invention;

FIG. 3 is an end sectional view of the mechanism with the primer shown in its out-of-circuit position in phantorn lines and in its incircuit position in solid lines; and

FIG. 4 is a side sectional view taken along line 4-4 of FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings wherein like reference characters designate identical or corresponding parts throughout the several views, and more particularly to FIG. 1 a thereof, an electrolytic device 10 for effecting movement of a primer is shown as including a cylindrical housing 12 formed of a dielectric material and defining an open ended chamber 14 at one end thereof. The general structure of a similar electrolytic device is disclosed in U.S. Pat. No. 3,205,321. The opposite end of housing 12 has formed therein a reduced diameter cylindrical opening or bore 16 which extends a limited distance within housing 12 to receive a plunger as will be described hereinafter. Housing 12 is provided with a conical end portion 20 having formed therein a coaxial central bore 22, which opens through the apex end of the end portion 20 and, with counterbores 24, 26 and 28 formed within cylindrical opening 16 serves to support various elements which will be described hereinafter. The electrolytic device 10 includes a plunger 30 disposed in housing 18 appropriately shaped to cooperate with other apparatus for moving an explosive primer into an in-circuit position as will be described hereinafter.

In FIG.1 b, an electrolytic circuit switch 10 having substantially the same overall structure as the electrolytic primer moving device 10 is partially shown as including a modified plunger 30' as will be described hereinafter.

Both plungers 30 and 30' include an annular shoulder 32 and a slot 34 formed in the end portion thereof, the slot 34 cooperating with an axial bore 36 adapted to hold a wire 38. The wire 38 extends through bore 36, counterbores 26 and 24 and bore 22 into chamber 14 and includes a head portion 40 which is larger in diameter than bore 22 and which acts as an anode as will be described hereinafter. An O-ring 42 engages the wall of bore 16 at counterbore 26 and wire 38 to form a fluid tight seal between counterbore 28 and counterbore 24. The distance between O-ring 42 and the head portion 40 of the wire 38 is greater than the maximum distance plunger 30 (or 30') will travel, as will be discussed in greater detail hereinafter, so that there is no break in the fluid seal upon movement of the plunger.

In assembling electrolytic device 10, the wire 38 is passed through bore 22 from chamber 14. O-ring 42 is placed in counterbore 26 and a washer 44 and a spring 46 are positioned in counterbore 28 with the washer 44 abutting O-ring 42 and spring 46 immediately adjacent thereto. The plunger 30 (30') is then placed and held in the housing 18 within spring 46 so that wire.38 extends through bore 36 into slot 34 where it is bent over as at 47 to secure the plunger 30. Plunger 30 (30) compresses spring 46 against washer 44 holding O-ring 42 in counterbore 26. The spring 46 also acts against shoulder 32 thereby urging the plunger outwardly causing the head portion 40 of wire 38 to abut against the conical end portion 20 which effectively seals the end of bore 22.

The plunger 30 of electrolytic primer moving device has an enlarged head portion 48 which, when in the position of FIG. 1 a, keeps an explosive primer in an out-of-circuit (unarmed) position as will be explained hereinafter. Plunger 30' of electrolytic switch 10' has an electroconductive surface 50 formed on its end which, when in the position of FIG. 1 b, maintains interrupted a circuit formed by leads 51 which are held fixed to the end of electrolytic switch 10 by a cupshaped member 53.

The electrolytic device 10 also includes a cathode 52 sealed to a circular cover plate 54 for chamber 14 by any suitable means and leads 56 and 58 for connecting the cathode and anode 40, respectively, in an electric circuit. A suitable electrolyte, such for example, as silver fluoborate, fills chamber 14.

The electrical circuitry of the present invention is shown diagrammatically in FIG. 2 and the operation of the device will be best understood by reference thereto wherein an electroresponsive explosive primer 57 is adapted to be initiated a predetermined time after the actuation of the device is accomplished by closure of a switch 59. When an ordnance device, such as a mine, is launched, switch 59 is closed by any well known means such, for example, as by pulling a safety pin 61 (FIG. 4) thereby causing a spring biased elongate member 97 to move against and close switch 59 whereupon a charging circuit is closed from the positive terminal of a battery 60 by way of conductor 62 and from the negative terminal thereof by way of conductor 64 to capacitor 66 which proceeds to acquire a stored electrical charge in a time controlled by the value of resistor 88. A timing circuit is also closed from the positive terminal of battery 60 via conductors 62 and 58 to which the anodes 40 of each of an electrolytic primer moving devide 10 and two electrolytic circuit switches 10 are connected. The circuit is continued through the electrolyte in each of the electrolytic devices, through the cathodes 52, to conductors 56, a set of variable resistors 74, a conductor 64, the closed switch 59 and back to the negative terminal of battery 60.

When this latter circuit is completed, electrolytic erosion of each of the anode head portions 40 takes place until the size of the head portion is reduced sufficiently to remove the restraint on the spring biased plungers 30 and 30' of the primer moving device 10 and switches 10', respectively. The variable resistors 74 are appropriately set to limit the current flow rate to cause the anode 40 of the electrolytic primer moving device 10 to erode before the anodes of the two circuit switches 10'. This causes plunger 30 to move outwardly under the force of spring 46 allowing the explosive primer 57 to move from an out-of-circuit position to an in-circuit position as will be described in greater detail hereinafter. In FIG. 2 the apparatus for performing the above operations is denoted by a dotted line 76. The primer 57 is caused to move such that its contacts 80 engage fixed contacts 78 in the discharge circuit. The

remaining variable resistors 74, i.e., those associated with the electrolytic timing switches 10' are set at equal values so that the head portions 40 of the electrolytic switches 10' will erode at equal rates thereby closing the circuit substantially simultaneously. Redundant switches 10 are provided primarily for safety purposes and more or less than two may readily be provided in the device. When either of anode head portions 40 erode, plunger 30' moves outwardly and the electroconductive plunger surface 50 completes the timing circuit across condenser 66 by simultaneously contacting leads 51. When either or both electrolytic switches 10' are closed, the capacitor 66, having acquired a stored electrical charge, discharges through the discharge circuit including conductor 82, conductor 84, the primer 57 and conductor 86. The electrical charge on capacitor 66 is sufficient to detonate the electroresponsive primer 57.

The device provides by virtue of the electrolytic mechanisms incorporated therein both an accurate time delay fuze and a time delay fuze which will operate under severe conditions after even the most adverse handling. Further, the delay between actuation of the device and its initiation can be extended to relatively great periods of time.

Referring now to FIGS. 3 and 4, the mechanism which causes the primer to move into its armed incircuit position is shown in greater detail. The primer 57 is disposed in a holder 90 which constrains it by reason of an inwardly turned flange 91 (FIG. 4), in such a manner that contacts of primer 57 may not be connected to the discharge circuit. This out-of-circuit position is shown in phantom in FIG. 3. The primer holder is integrally formed at one end of an elongate shutter member 92 and forms a through bore 99 which allows the contacts 80 of primer 57 to be exposed rearwardly of shutter member 92. An integral protruding extension 93 is formed on holder 90 and extends beyond the end portion 95 of an elongate member 97. The shutter member 92 is pivotally connected at its end opposite primer holder 90 to mechanism housing 96 at pivot 94. Further, shutter member 92 is fixed in its outof-circuit position against the force of a spring 98 connected to the shutter member 92 at one end and to the mechanism housing 96 at its other end by the cooperation of the plunger head portion 48 of the electrolytic primer moving device 10 which acts as a detent and an arcuate surface 100 formed on the end of the shutter member 92 opposite the pivot point 94. As described hereinbefore, after switch 58 is closed anode 40 in the electrolytic primer moving device It) begins to erode and upon reaching a sufficiently small size releases the spring biased plunger 30 which allows the plunger head portion 48 to move forward to the position shown in FIG. 4. Upon termination of the cooperation between the plunger head portion 48 and the arcuate surface 100, the shutter member 92 is urged into the in-circuit position as depicted in FIG. 4 wherein fixed contacts 78 engage contacts 80 of the electroresponsive primer 57 as the primer 57 moves into the solid-line position of FIG. 3 thereby placing primer S7 in the discharge circuit and arming the device. Should electrolytic switches operate prematurely, extension 93 would interfere with elongate member end portion 95 thereby preventing the primer 57 from becoming electrically coupled within the circuit.

Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described herein.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. A time delay firing device comprising:

an electroresponsive primer;

a source of electrical energy;

a normally open charging circuit including electrical energy storage means;

a selectively operable switch adapted to be coupled to said energy source and said charging circuit;

a normally open timing circuit adapted to be coupled to said switch including a first electrolytic timing device for selectively coupling said electroresponsive primer to a discharge circuit after a first length of time and a second electrolytic timing device for closing a discharge circuit after a second length of time; and

a discharge circuit including said electrical energy storage means and said second electrolytic timing device,

whereupon the closing of said switch completes said charging circuit to energize said energy storage means and simultaneously closes said timing circuit thereby initiating the timing sequences of said electrolytic timing devices whereby after elapse of said first length of time said primer is coupled to said discharge circuit and at the expiration of said second length of time said timing circuit is completed permitting said stored energy to discharge into and initiate said primer.

2. A time delay firing device as recited in claim 1 wherein said second electrolytic timing device includes:

a housing divided into a plunger housing and an electrolyte chamber;

a cathode disposed in said electrolyte chamber;

a passage connecting said plunger housing and said electrolyte chamber;

an anode having an enlarged head portion wider than said passage normally disposed in said electrolyte chamber and an elongate portion extending through said passage;

a plunger located in said plunger housing attached to said anode having an electrically conductive end surface; and

resilient means acting between said plunger housing and said plunger for urging said plunger out of said plunger housing until said electrically conductive end Surface completes a circuit.

3. A time delay firing device as recited in claim 1 wherein said first electrolytic timing device is coupled to a resiliently biased shutter device adapted to move said primer from a first position out of said discharge circuit to a second positioned coupled to said discharge circuit 4. A time delay firing device as recited in claim 3 wherein said first electrolytic device is coupled to a resiliently biased shutter device which holds the primer comprising said first electrolytic device comprises:

a housing divided into a plunger housing and an electrolyte chamber;

a cathode disposed in said electrolyte chamber;

a passage connecting said plunger housing and said electrolyte chamber;

an anode having an enlarged head portion wider than said passage normally disposed in said electrolyte chamber and an elongate portion extending through said passage;

an elongate plunger located in said plunger housing attached to said anode and having an enlarged discshaped end portion normally cooperating with said shutter device to prevent said resiliently biased shutter device from moving said primer from sid first position to said second position; and

resilient means between said plunger housing and said plunger for urging said plunger out of said plunger housing thereby moving said enlarged end portion in a manner to permit said shutter device to move said primer from said first position to said second position.

5. A time delay firing device as recited in claim 4 wherein said resiliently biased shutter device comprises:

a member pivotably mounted at one end to the firing device housing so as to be movable in a plane perpendicular to the longitudinal axis of said plunger of said first electrolytic device;

means for holding said primer fixedly attached to said member;

said member having an arcuate shaped end portion adapted to cooperate with said enlarged plunger end portion; and

second resilient means acting between said member and said first housing for urging said member from said firing device position to said second position when said plunger is moved out of the plunger housing thereby ending said cooperation between said shutter device and said enlarged plunger end portion. 

1. A time delay firing device comprising: an electroresponsive primer; a source of electrical energy; a normally open charging circuit including electrical energy storage means; a selectively operable switch adapted to be coupled to said energy source and said charging circuit; a normally open timing circuit adapted to be coupled to said switch including a first electrolytic timing device for selectively coupling said electroresponsive primer to a discharge circuit after a first length of time and a second electrolytic timing device for closing a discharge circuit after a second length of time; and a discharge circuit including said electrical energy storage means and said second electrolytic timing device, whereupon the closing of said switch completes said charging circuit to energize said energy storage means and simultaneously closes said timing circuit thereby initiating the timing sequences of said electrolytic timing devices whereby after elaPse of said first length of time said primer is coupled to said discharge circuit and at the expiration of said second length of time said timing circuit is completed permitting said stored energy to discharge into and initiate said primer.
 2. A time delay firing device as recited in claim 1 wherein said second electrolytic timing device includes: a housing divided into a plunger housing and an electrolyte chamber; a cathode disposed in said electrolyte chamber; a passage connecting said plunger housing and said electrolyte chamber; an anode having an enlarged head portion wider than said passage normally disposed in said electrolyte chamber and an elongate portion extending through said passage; a plunger located in said plunger housing attached to said anode having an electrically conductive end surface; and resilient means acting between said plunger housing and said plunger for urging said plunger out of said plunger housing until said electrically conductive end surface completes a circuit.
 3. A time delay firing device as recited in claim 1 wherein said first electrolytic timing device is coupled to a resiliently biased shutter device adapted to move said primer from a first position out of said discharge circuit to a second positioned coupled to said discharge circuit.
 4. A time delay firing device as recited in claim 3 wherein said first electrolytic device is coupled to a resiliently biased shutter device which holds the primer comprising said first electrolytic device comprises: a housing divided into a plunger housing and an electrolyte chamber; a cathode disposed in said electrolyte chamber; a passage connecting said plunger housing and said electrolyte chamber; an anode having an enlarged head portion wider than said passage normally disposed in said electrolyte chamber and an elongate portion extending through said passage; an elongate plunger located in said plunger housing attached to said anode and having an enlarged disc-shaped end portion normally cooperating with said shutter device to prevent said resiliently biased shutter device from moving said primer from sid first position to said second position; and resilient means between said plunger housing and said plunger for urging said plunger out of said plunger housing thereby moving said enlarged end portion in a manner to permit said shutter device to move said primer from said first position to said second position.
 5. A time delay firing device as recited in claim 4 wherein said resiliently biased shutter device comprises: a member pivotably mounted at one end to the firing device housing so as to be movable in a plane perpendicular to the longitudinal axis of said plunger of said first electrolytic device; means for holding said primer fixedly attached to said member; said member having an arcuate shaped end portion adapted to cooperate with said enlarged plunger end portion; and second resilient means acting between said member and said first housing for urging said member from said firing device position to said second position when said plunger is moved out of the plunger housing thereby ending said cooperation between said shutter device and said enlarged plunger end portion. 